1. Field of the Invention
The present invention relates to a motor having a rotor embedded with permanent magnets and a method of manufacturing the motor.
2. Discussion of Background
When permanent magnets of a sintered type are embedded in a motor, the motor is manufactured by inserting permanent magnets into slits formed in a rotor core and filling the gaps caused by errors in their form by a filler and/or a bonding agent and then fixing the permanent magnets to the rotor core by mechanically joining the permanent magnets to the rotor core using joining methods like bolts and nuts, methods have obstructive factors in forming the permanent magnets which reduce productivity of the motor assembly. Further, in the case where the permanent magnets are formed by injecting a powdered material constituting permanent magnets, it is necessary to introduce a rotor under a high temperature of 500.degree. C. or more for a long period, which requires expensive equipment and reduces reliability due to residual stress and deformation caused by the application of heat to the rotor, and so on.
FIG. 14 is disclosed in JP-A-10-112946 to solve the above-mentioned problems, wherein a structure of rotor of a brush-less d.c. motor with embedded permanent magnets is shown. In FIG. 14, permanent magnets formed by bonding magnetic powders having a hard magnetic phase and a resin with a soft magnetic phase are inserted in slots 2 formed at four positions in a rotor core 1; and thereafter the permanent magnets are fixed to the rotor core 1 by adhering or mechanically joining using bolts and nuts.
However, failures caused by peeling-off, cutout, and so on occurred to the permanent magnets during high revolutions for a long period even though such joining methods were used.